1. Field of the Invention
The present invention relates to a temperature control system which controls the temperature of a heater mounted in a gas sensor in such a manner as to keep the heater at a substantially constant temperature.
2. Description of the Prior Art
A known gas sensor is provided with a heater for heating a gas concentration measuring part to a suitable temperature at which the gas concentration measuring part functions efficiently and accurately. To control the temperature of the heater, it has been tried to sense the actual temperature of the heater with a temperature sensing element. The temperature sensed by the sensing element is compared with a predetermined temperature at a comparator. The control is carried out such that when the sensed temperature is lower than the predetermined temperature, a relay switch is closed to connect a source of electric power to the heater, while, when the sensed temperature is higher than the predetermined temperature the relay is opened to disconnect the heater from the source of electric power. The temperature sensing element is embedded in a base plate wherein the heater is disposed. However, it has been found difficult to embed the temperature sensing element in the base plate.